Electrical resistance



July 18, 1933. J. GABRIEL 1,918,259

ELEGTRI CAL RES I STANCE Filed Oct. 25, 1930 2 Sheets-Sheet '1 FIG?uwsuroe J. C. GABRIEL ATTORNEY y 1933. J. c. GABRIEL ELECTRICALRESISTANCE Filed 001:. 23, 1930 2 Sheets-Sheet 2 FIG. 5

FIG. 6

RE C.

GEN.

. INVENTOR J. C. GABRIEL ATTORNEY provide means present in its vicinitPatented July 18, 1933 UNITED STATES PATENT OFFICE JOHN C. GABRIEL, OFNEW YORK, N. Y., ASSIGNOR T0 BELL TELEPHONE LABORATORIES,

INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK ELECTRICALRESISTANCE Application filed October 23, 1930. Serial No. 490,594.

This invention relates to resistance wind ings and particularly to thatform of resistance element Which has very low distr buted capacity andsubstantially no self-1nductance and therefore acts in an electricalcircuit as a, pure resistance.

One of the objects of the invention is to provide a resistance elementwhich has the characteristics mentioned above and whlch is very simpleand easily constructed.

A further object of the invention is to provide a resistance winding ofthe zigzag type which does not require a special form of supportingmember. Heretofore it has been the practice to employ supporting membersprovided with pins, hooks, lugs, tongues, holes, grooves, or the likefor receiving the loops of wire. In the present lnvention a plain blockor card of insulating material is employed for supporting the windingand the latter is retained thereon in a manner which will hereinafter bedescribed.

-A further object of the invention is to provide a resistance winding ofthe zlgzag type in whichthe turns of wire are automatically spaced fromeach other any predetermined distance when the winding is applied to thesupporting member.

A further object of the invention 1s to provide a resistance winding ofthe zigzag type in which, on a supporting member of g ven size, theturns of wire may have any desired length up to a length equal to thetransverse perimeter of the supporting member.

, A further object of the invention is to provide a resistance windingwhich can be used as an attenuator in electrical circuits in which fieryhigh frequency alternating currents are present without the productionof counter-electromotive forces due to selfinductance of the winding.

A further ob'ect of the invention is to for protecting the resistanceelement from magnetic fields which may be in order that no currentsshall flow in t e winding other than those applied to its terminals.

The novel features which are believed to characterize the invention areset forth with particularity in the appended claims. The

invention itself, however, both as to its organization and constructiontogether with further objects and advantages thereof will best beunderstood b' reference to the following description ta en in connectionwith the accompanying drawings in which Fig. 1 is aside view and Fig. 2a plan view showing a resistance element wound in accordance with theinvention. Fig. 3' is a perspective view partly exploded showing thepreferred method of mounting the resistance units. Fig. 4is a viewsimilar to Fig. 1 showing a modified winding arrangement. Fig. 5 1s aperspective view showing one of the assemblies of Fig. 3 inounted in ashielding container, and a switch for connecting the unit to a circuit.Fig. 6 is a schematic diagram of a circuit showing several assemblies inuseas attenuators.

Referring to Figs. 1 and 2, the reference numeral 1 indicates a flatcard or block which receives and supports the resistance winding 2. Thecard or block 1 may be of any suitable insulating material such asbakelite, a phenolic condensation product, and may be of any desiredlength, width or thickness. Starting near one end of the card or blockthe conductor 2 is wound (with the aid of cord 3 as will be described)back and forth across the surface of the card in zigzag arrangement. Atthe same time that the con ductor is being wound on the card acontinuous retaining cord 3 of insulating material such as cotton orlinen thread or twine is wound on the opposite face of the cardbeginning at the same end. As the cord and conductor are brought to anedge of the card, one is looped around the other and they are thenbrought to the opposite edge of the card and are again interlooped. Fromthis it may be seen that each loop of the conductor engages acorresponding loop in the retainin cord. The conductor and retainingcord form similar windings upon the card or block and each engages allof. the loops in the other.

Although the interloopings of conductor and cord have been shown inFigs. 1 and 2 as spaced apart, it will be understood that the turns maybe arranged one against the other, but out of electrical contact,without departing from the spirit of this invention. The thickness ofthe retaining cord will determine the spacing of the turns of theconductor and if the diameter of the retaining cord is large comparedwith that of the conductor, adjacent strands of the conductor will tendto be spaced from each other even though adjacent strands of theretaining cord are applied as closely as possible and are squeezedtogether.

In Figs. 1 and 2 the conductor is shown as extending across only oneface of the block or card but it will be understood that the inventionis not confined to this arrangement. The turns of the conductor may haveany desired length and the extent of each turn is limited only by theperimeter of the block. The turns of the conductor may extend acrossjust a portion of one face of the card, as shown in Fig. 4. They mayalso extend across two or three faces as desired; however, it is best toconfine the turns 'to only one face of the card in order that thewindings may have no cross-sectional area, thus obviating inductancefrom this source. In any case, the turns of the retaining cord willextend across those portions of the surface of the card across which noturns of the conductor extend.

When current is applied to a conductor arranged as described above, theflow of current in adjacent transverse lengths of the conductor will bein opposite directions. Any magnetic field that is produced by the flowof current in any transverse length of the conductor will be opposed andnullified by the magnetic field produced by the flow of current in theopposite direction in the adjacent transverse lengths of the conductors.From this it may be seen that the algebraic sum of the inductive effectsof all the turns of the conductor will be approximately zero and theresistance unit will have substantially no self inductance.

Fig. 3 shows an arrangement for mounting the resistance element shown inFig. 1. A low impedance terminal band 4 is applied to one end of thecard or block 1 of the resistance element 18 and is secured thereto bythe rivets 5. The band 4 engages the block and retains one of the endsof the cord 3 which is disposed between the band and the block. One endof the conductor 2 may be soldered to the terminal band 4. The band hasformed integrally therewith a tab 6 by means of which the conductor 2may be connected in an electrical circuit. The card or block 1 hassecured to its opposite end by rivets 5 a member 7 comprising terminalbands 8 and 9 angularly disposed with respect to each other. The ends ofthe conductor 2 and the cord 3 are retained by the member 8 in a mannersimilar to that of the terminal band 4. Another resistance unit 19constructed in accordanee with the invention has attached to one endthereof a band member 4 and to the other end a terminal band 10 providedwith a tongue 11. The terminal band 9 of the member 7 receives one endof a third resistance unit 14, wound in accordance with the invention,and the. tongue 11 of the terminal 10. One end of the conductive windingof resistance unit 14 is soldered to the terminal band 9. The tongue 11and resistance unit 14 are secured to the terminal band 9 by rivetspassing through the holes 17. conductive member 15 of any desired lengthhas integrally formed therewith a terminal band 16 which is secured tothe resistance unit 14. The other end of the coductive winding ofresistance unit 14 is soldered to the terminal band 16. The terminalbands 4, 8, 9, 10 and 16 and their associated elements 6, 7, 11 and 15are formed of a highly conductive material such as copper. The assemblydescribed above and shown in Fig. 3 is a Y-shaped arrangement in whichtwo of the resistance units having external terminals 6 are connected inseries through the member 7, and in which the resistance unit 14 mayform a shunt to ground through the member 15, which is preferablygrounded.

It is obvious that the resistance assembly such as that shown in Fig. 3is adaptable for use in a great many electrical circuits and fornumerous purposes. The assembly was developed for use as a highfrequency attenuator. It is proposed to use one or more of theseassemblies shown in Fig. 3 as attenuators in testing vacuum tubecircuits at a frequnecy of 20 megacyeles. At frequencies of that orderof magnitude, selfinductance in the attenuator would produce veryobjectionable efi'ects. Attenuator units constructed as described andshown, are well suited for use at such frequencies by reason of the factthat they have little or no self inductance. In practice it is proposedto use No. 46 American wire gauge insulated manganin wire as theconductive winding of the resistance pad that enters into the assemblyshown in Fig. 3. Sufiicient wire will be used in each of the resistanceelements 18 and- 19 to provide resistance of 58.80 ohms in each winding.Sufiicient wire to provide 14.540 ohms resistance will be used intheresistance element 14. It is important that the terminal bands 4, 8 and10 and 16 and their associated elements 6, 7, 11 and 15 be of moderatelyheavy copper and that the conductive winding be securely soldered to theterminal band in order that the impedances of these terminals shall benegligible in comparison with the impedances of the windings.

When resistance elements are used as attenuators in electrical circuitsin which very high frequency alternating currents are flowing, it isnecessary that the resistance elements be protected from electrical ormagnetic disturbances that may be present in the vicinity of theapparatus. Protection against such disturbances is accomplished byshielding. Fig. 5 shows an arrangement for shielding one of theresistance assemblies shown in Fig. 3. A quadrangular metallic shieldingcontainer 20 is provided. It may be of any suitable conductive materialsuch as cooper or aluminum. One of the resistance assemblies is disposedin the shielding container in such position that no portion of theassembly except the member 15 shall be in contact with any portion ofthe shielding container. The member 15 may be employed for mounting theresistance assembly in the compartment and it may terminate at the wallof the container 20 and be secured by rivets as shown in Fig. 5.

A double-pole double-throw key switch 21 is mounted inside the shieldingcontainer 20 and has its operating lever 22 extending through anaperture in the shielding container so as to be operable from outside.The key switch 21 has six terminals. The dimensions of the shieldingcontainer 20 are such that when the resistance assembly and key switchare mounted in the container the terminal tabs 6 can be soldereddirectly to two of the terminal prongs of the switch 21 and intermediatelead wires are not required. Leads 23 for connecting these resistanceassemblies to an electrical circuit are connected preferably bysoldering to the two central terminal prongs of the switch. A lowimpedance conductive member 24 is connected across the remaining twoterminals. It will be apparent that with this switching arrangement theresistance elements 18 and 19 or the short-circuiting member 24 may beinserted in the path through the lead 23 or that path can remain open.The shielding container 20 is provided with apertures 25 through whichthe leads 23 may pass and these apertures should be so positioned withrespect to the terminal prongs of the key switch that the portion of theleads inside the shielding container may be as short as possible. Theapertures 25 should be sufliciently large to permit the lead 23 to passthrough without touching the wall of the shielding container.

Fig. 6 shows a schematic diagram of a circuit in which a plurality ofthe assemblies shown in Fig. 5 are employed as attenuators. Referencenumeral 26 indicates an oscillation generator capable of producing a 20megacycle frequency alternating current or a current of any desiredfrequency. The oscillation generator 26 works into a vacuum tubeamplifier 27 and the alternating current output of the amplifier ismeasured by the measuring instrument 28 connected to the rectifier 29.The alternating current from the amplitier 27 is attenuated any desiredamount by means of a plurality of the switch controlled resistanceassemblies shown in the shielding container in Fig. 5. For this purposea plurality of the shielding containers 20 each containing one of theswitch controlled resistance assemblies and having leads 23 passing fromone container to the next are provided. As shown by the dotted lines inFig. 6 one shielding container 20 divided into a plurality ofcompartments by the shielding partitions 30 may be provided instead of aplurality of individual shielding compartments such as the one shown inFig. 5. Each of the compartments contains one of theswitch controlledresistance assemblies and the leads 23 may pass from one compartment tothe next. After the alternating current from the amplifier 27 has beenattenuated it is applied to the input of a radio receiving set 31 or anyother vacuum tube circuit that is to be tested. A measuring instrument32 is connected to the output of the radio receiving set or vacuum tubecircuit for indicating the magnitude of the output of the circuit.

While a sin le embodiment of the invention has been ilTustrated anddescribed, the invention is not limited to the specific arrangementshown as variations may be made in the apparatus employed and itsassembly and arrangement without departingfrom the scope of theinvention as set forth in the claims.

What is claimed is:

1. A resistance unit comprising a card of insulating material, aflexible conductor carried on one side of the card in zigzag arrangementtransversely thereon and retaining means on the other side of the card,said means comprising a continuous flexible cord interlaced withconsecutive loops of said conductor, the diameter of the cord beinglarge compared with that of the conductor, and adjacent turns of theconductor being spaced from each other b an amount determined by thethickness of tlie retaining cord.

2. In a high frequency attenuator, a resistor comprising a flexibleconductor arranged transversely on only one side of a card in a zigzagmanner, the card being composed of dielectric material, and means forretaining the conductor in its zigzag position, said means comprising acontinuous cord arranged transversely on the opposite side of the cardin a zigzag manner, the loops of the cord being interlaced with similarloops of the conductor.

JOHN C. GABRIEL.

